Mutual phenomena of Galilean sattelites (Dec 2002 .. Apr 2003)

Eclipse of Io by Europa, dec30, 2002
Occultation of Ganymede by Callisto, dec30, 2002

Every 6 years or so, the Earth and Sun intersect the orbital plane of Jupiter's sattelites. In these periods, we can observe occultations and  eclipses of the Galilean sattelites. The current period (which lasts through April 2003) is particularly good for the observations, as Jupiter is high in the sky most of the night.

IMCCE in France organises a campaign of observations of the mutual events. The link to the campaign's page is here. This page contains very good information about the finer points on making these observations.

The equipment i use for the observations is as follows:
The camera is normally used with a NIR filter (RG695), which dims the very bright sattelites, and also reduces the atmospheric scintillation, which is the dominant error source in the measurements.

Observing an even takes around half an hour, during which about 400 ccd frames are taken. The framing is done so that the frame contains both the target sattelite(s) and at least one sattelite that does not participate in the event and is used for reference. Exposures are of the order of 1-2 seconds.

The reduction of data consists of three steps: first, the frames are dark-substracted and flat-fielded. Then, using the (semi) automatic routine from my cx software, the magnitudes of the images sattelites is measured, and output into a data file. After a quick check of the data (using gnuplot), the file is sent to IMCCE. The people at IMCCE extract the exact time of the event by fitting the teoretical light curve to the data.